Device for regulating compressors or aspirators

ABSTRACT

In a delivery conduit for a compressor or an aspiration conduit for an aspirator, which connects the compressor or the aspirator to a closed environment, a first valve is inserted, and opening and a closing of which is commanded by a temperature of an external environment. The valve is normally closed for external temperatures which are lower than a predetermined level and open, placing the conduit in communication with the outside environment, when the external temperature exceeds the predetermined level.

BACKGROUND OF THE INVENTION

[0001] Specifically, though not exclusively, the invention is usefullyapplied in dental aspirating apparatus.

[0002] In the following description and in the accompanying figuresreference is made to an aspirator (a suction or “vacuum” pump) but allof the description could also be applied to compressors.

[0003] Aspirators are much-used in dental aspiration plants where adepression has to be created in connection with suction tubes.

[0004] It is well-known that the coils of electric motors actuating theaspirators are subject to heating-up: this heating-up increases as thecurrent supply absorbed by the motor increases, which in turn increasesin line with the degree of depression required.

[0005] To limit this heating-up, a valve is usually provided, usuallyarranged in the aspiration conduit connecting the aspirator to theenvironment in which the depression is to be created. When the valve isopened it places the aspiration conduit (or the above-mentionedenvironment) in connection with the outside. This valve is opened when apredetermined pressure difference is reached between the outsideenvironment and the inside environment, which corresponds to apredetermined electrical current which crosses the motor coils. In thisway, without stopping the machine, excessive heating-up is avoided dueto over-heating of the motor coils.

[0006] The problems encountered with compressors when the internalpressure increases are very similar.

[0007] The heat produced by aspirators is dispersed in the outsideenvironment. For this reason the manufacturers always recommend that themachines be located in well-aired and cool places in order for themachine to perform optimally. Unfortunately, for reasons of space,aesthetic preference, or in order to avoid any irritation that might becaused by the admittedly low noise level of aspirators, these machinesare often arranged in small and closed places, generally lacking in air;sometimes they are even kept away from the outside environment.

[0008] In these conditions, the heat dispersed by the aspirators causesconsiderable build-up of heat in the surrounding atmosphere, with aconsequent heating of the aspirator to beyond realistic limits, causingdeterioration in its performance or even faulty functioning and, inparticularly grave cases, or in the absence of devices blocking themotor when it reaches dangerous temperatures, a fire hazard. All of theabove can happen without the electric current in the coils reachinglevels which correspond to a depression level warranting theinterjection of the above-cited valve, which would reduce electriccurrent absorption and thus reduce the heat produced by the machine.

[0009] If there is a thermal cut-off protection for the motor, afrequent case, the motor is shut down before the aspirator reaches itsmaximum potential. To prevent machine shut-down, or to reduce itsoccurrence to an absolute minimum, sometimes the manufacturersthemselves calibrate the pressure-differential valves to more prudentlevels, thus in effect lowering the potential of the machine and doingan injustice to those users who carefully follow the instructionsprovided with the machine and locate the aspirator in a correct ambiencein order to allow plenty of ventilation.

[0010] The main aim of the present invention is to obviate theabove-cited drawback in the prior art, by providing a device forregulation of compressors and aspirators which enables the machines tofunction at maximum potential when the conditions of the outsideenvironment are optimal, but which reduces the machine's performancelevel when there is an imperfect surrounding environment.

[0011] A further aim of the invention is to prevent excessive heating-upof the machine without having to shut the machine down.

[0012] An advantage of the device is that it can be applied easily toexisting machines. These aims and more besides are all attained by theinvention as it is characterized in the claims that follow.

SUMMARY OF THE INVENTION

[0013] In a delivery conduit for a compressor or an aspiration conduitfor an aspirator, which connects the compressor or the aspirator to aclosed environment, a first valve is inserted, and opening and a closingof which is commanded by a temperature of an external environment. Thevalve is normally closed for external temperatures which are lower thana predetermined level and open, placing the conduit in communicationwith the outside environment, when the external temperature exceeds thepredetermined level.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Further characteristics and advantages of the present inventionwill better emerge from the detailed description that follows, of apreferred but nonexclusive embodiment of the invention, illustratedpurely by way of example in the appended figures of the drawings, inwhich:

[0015]FIG. 1 is a diagram of an aspirator of the type of the invention;

[0016]FIG. 2 is a detail of FIG. 1, in section and in enlarged scale,relating to the valve of the device of the invention;

[0017]FIG. 3 is a view in the direction indicated by arrow A in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS.

[0018] With reference to the figures of the drawings, 1 denotes in itsentirety an aspirator, constituted by a pump 1 a and an electric motor 1b, from an aspiration conduit 2 originates and connects the aspirator toa closed environment 3. The aspirator extracts air from the closedenvironment 3 through the conduit 2. A discharge conduit 2 a isconnected to the aspirator 1 for removing the air aspirated there-from.

[0019] Leading out of the aspiration conduit 2 there is a cylindricalsleeve 5, a first end 5 a of which is connected to the aspirationconduit 2 and a second end of which 5 b is connected to the outsideenvironment. An annular seating 9 is afforded in the sleeve 5, to whichan obturator 7, predisposed inside the sleeve 5, is associated.

[0020] The obturator is normally in a closed position, i.e. pressedagainst the seating 9, in which position the obturator 7 preventspassage of air through the sleeve 5.

[0021] The obturator 7 is kept pressed against the seating 9 by anelastic element, in the illustrated embodiment a helix spring 8, whichis preloaded at a predetermined load, and is loaded against the openingof the obturator 7. A chamber is afforded inside the obturator 7, whichchamber 10 is filled with a material having a high heat-dilationcoefficient, for example a thermometric liquid. An end of a rod 11projects from the chamber 10, which rod 11 is slidable in an axialdirection and another end of which is inserted in the chamber 10, sunkin the thermometric liquid. The section of the exit hole of the rod 11from the chamber 10 is completely occupied by the section of the rod 11itself, in order to prevent any exiting of material from the chamber 10.A striker element 12, fixed with respect to the sleeve 5, is constrainedto the end of the rod 11 projecting from the chamber 10. This strikerelement 12, which in the figures is illustrated as a metal bar arrangeddiametrically and constrained to the ends of the external surface of thesleeve 5, is arranged in such a way that it obstructs an externalwisesliding by the rod 11. For this purpose the striker element 12 isarranged above the end of the rod 11 which exits from the chamber 10.

[0022] The above-described device realises a first valve 4 and a secondvalve 6 which have a common seating and obturator, and therefore whichboth act in opening or closing the connection between the aspirationconduit 2 and the outside environment. The two valves are, however,differently controlled and are independent from each other, and arefunctionally different and distinct. The opening and closing of thefirst valve 4 is commanded by the temperature in the outsideenvironment. When the outside temperature increases, the materialcontained in the chamber 10 dilates and pushes the rod 11 externalwise;the rod 11 then pushes against the striker element 12 and thus pushesthe obturator 7 away from the seating 9, opening the valve 4 and placingthe aspiration conduit 2 in communication with the outside environment.The quantity of thermometric material, the section of the rod 11 and itsinitial distance from the striker element 12 are calculated in such away as to cause an opening of the valve when the external temperaturerises above a predetermined level, normally comprised between 45° C. and55° C.

[0023] The opening and closing of the second valve 6 is commanded by thedifference between the closed environment 3 and the outside environment.When this difference, to which a precise absorption of electric currentcorresponds, and therefore a precise coil temperature, overcomes theload on the spring 8, the obturator 7 distances from the seating 9 andopens the valve, setting the aspiration conduit 2 in communication withthe outside environment. This functioning of the valve 6, activated by amotor coil temperature of between 90° C. and 120° C., is similar to thefunctioning of known valves mounted on aspirators of known type.

[0024] When, in any one of the above-described ways, the connectionbetween the aspiration conduit 2 and the outside environment is opened,the absorption of electric current by the aspirator motor is drasticallyreduced, as is the performance of the motor (which the user will noticein the guise of a fault), and the production of heat by the motor. Thereduction of heat by the machine and/or an intervention by the user,i.e. making more cool air available to the machine in order to reducethe outside temperature in the surrounding atmosphere, cause the valvesto close and bring the machine back into conditions of normal operation,without having to shut the machine down. The above-described devicebehaves as a normal, known-type overpressure valve for the currentabsorbed by the motor when the temperature is within normal parameters,while it becomes an added protection cutoff when the temperature limitsare exceeded.

[0025] If the device is applied not on an aspirator but on a compressor,the conformation of the device will be slightly different. The devicewill be located on the delivery conduit, the obturator will openexternalwise and the rod will move in an opposite direction against aninternal striker element; but its functioning will be altogether similarto what is described above.

[0026] It is worth noting that the two valves could also be constructeddifferently to one another, inasmuch as they could each have their ownobturator and seating. The described and illustrated conformationpermits greater constructional economy as well as a greater operatingsafety.

What is claimed: 1). A device for regulating compressors or aspirators,comprising, in the case of a compressor, a delivery conduit, and in thecase of an aspirator, an aspiration conduit which conduit connects thecompressor or aspirator to a closed environment, through which conduitair is introduced, in the case of a compressor, or extracted, in thecase of an aspirator, to or from the closed environment: wherein thedevice also comprises a first valve arranged between the conduit and anoutside environment which is normally closed when a temperature of theoutside environment is below a predetermined temperature and open when atemperature of the outside environment is above a predeterminedtemperature, placing the conduit in communication with the outsideenvironment. 2). The device of claim 1, comprising a second valve ofknown type which is located between the conduit and the outsideenvironment, an opening and closing of which second valve is controlledby a predetermined pressure differential between the closed environmentand the outside environment, wherein the first valve and the secondvalve have an obturator in common, an opening and closing movement ofwhich are controlled independently both by a reaching of thepredetermined pressure differential between the closed environment andthe outside environment and by a reaching of the predeterminedtemperature of the outside environment. 3). The device of claim 2,wherein: the first valve and the second valve are made in a sleeve, afirst end of which is connected to the conduit and a second end of whichis connected to the outside environment, and in which sleeve a seatingis made for the first valve and the second valve, and which sleevehouses the obturator; an opening of the obturator being opposed by anelastic element; a chamber being afforded internally of the obturator,which chamber is filled with a material having a high coefficient ofheat dilation and from an end of which chamber an end of a rod projects,which rod is slidable in an axial direction, and another end of whichrod is inserted in the chamber; there being also a striker element,fixed with respect to the sleeve, which striker element is conformed andarranged in such a way as to oppose an externalwise sliding of the rod.